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From John Lilley <john.lil...@redpoint.net>
Subject RE: HDFS performance with an without replication
Date Fri, 20 Sep 2013 00:14:17 GMT
Thanks, that makes sense.

-----Original Message-----
From: Harsh J [mailto:harsh@cloudera.com] 
Sent: Sunday, September 15, 2013 12:39 PM
To: <user@hadoop.apache.org>
Subject: Re: HDFS performance with an without replication

Write performance improves with lesser replicas (as a result of synchronous and sequenced
write pipelines in HDFS). Reads would be the same, unless you're unable to schedule a rack-local
read (at worst
case) due to only one (busy) rack holding it.

On Sun, Sep 15, 2013 at 10:38 PM, John Lilley <john.lilley@redpoint.net> wrote:
> In our YARN application, we are considering whether to store temporary 
> data with replication=1 or replication=3 (or give the user an option).  
> Obviously there is a tradeoff between reliability and performance, but 
> on smaller clusters I'd expect this to be less of an issue.
> What is the difference in write performance using replication=1 vs 3?  
> For reading I'd expect the performance to be roughly requivalent.
> john

Harsh J

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